Field
The present invention relates generally to electric energy storage devices, and more specifically, to a method of pre-doping an electrode of an energy storage device with ionic species.
Description of the Related Art
Lithium ion capacitors may be used to power a diverse range of electronic devices, including for example in wind power generation systems, uninterruptible power source systems (UPS), photo voltaic power generation, and/or energy recovery systems in industrial machinery and transportation systems. Lithium ion capacitors can have a variety of shapes (e.g., prismatic, cylindrical and/or button shaped). A lithium ion capacitor (LIC) can include an anode and a cathode immersed in an electrolyte which provides a transport of ionic species between the anode and the cathode. Lithium ion capacitors can be a type of hybrid ultracapacitor, exhibiting significant electrostatic and electrochemical energy storage. For example, electrical charge can be stored at an electrical double layer formed at an interface between an electrolyte and an electrode (e.g., between a lithium ion capacitor electrolyte and a lithium ion capacitor cathode). Electrical energy in a lithium ion capacitor may also be stored through adsorption of ionic species into an electrode (e.g., adsorption of lithium ions into a lithium ion capacitor anode). Lithium ions can be incorporated into the anode of the lithium ion capacitor through a pre-doping process.
A solid-electrolyte interphase (SEI) layer may form adjacent a surface of a lithium-ion capacitor anode. A solid-electrolyte interphase layer may form during an anode pre-doping process. For example, the solid-electrolyte interphase layer may form at least in part due to an electrochemical reaction at the anode surface involving an electrolyte solvent and/or an electrolyte salt. The solid-electrolyte interphase layer may electrically insulate the anode while allowing an ionic transport to the anode.